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. 1998 Mar 31;95(7):3685–3689. doi: 10.1073/pnas.95.7.3685

Figure 1.

Figure 1

Resource allocation tradeoffs in the development of butterfly wings and beetle horns. Species illustrated are P. coenia (a) and O. taurus (d). One or two hind wing imaginal discs were excised from caterpillars of P. coenia during the second day of the final larval instar and the compensatory responses of fore wings and other tissues was measured in the adults that developed from these larvae. (b) Animals with excised hind wings developed disproportionally large fore wings for their body sizes (one-way analysis of covariance, with body dry weight as covariate F = 51.010, P = 0.0001), and the magnitude of this effect depended on the number of hind wings removed. (c) Removal of hind wings also affected other traits. Males with reduced number of hind wings developed disproportionally large thoracic dry weight and foreleg femur length, but the relative dry weights of the head and abdomen were unaffected (F values shown are for the effect of hind wing removal in one-way analysis of covariance, with body dry weight as covariate). Developmental time was not affected by the surgery [duration of final larval instar (mean ± SD): sham-operated controls, 6.50 ± 0.86 days; one wing removed, 6.42 ± 0.99 days; two wings removed, 6.94 ± 0.68 days). In O. acuminatus, male horn size was altered through artificial selection. After seven generations of selection, males selected for relatively long horns had significantly longer horns than males selected for relatively short horns (25). (e) Heritable changes in the relative length of male horns resulted in negatively correlated changes in the sizes of male eyes (one-way analysis of covariance with body size, measured as width of prothorax, as the covariate, F = 330.355, P = 0.0001). (f) Compensation only involved the compound eyes; the relative sizes of other structures were unaffected by selection on horn size (F values for one-way analysis of covariance for the effect of artificial selection on horn length with prothorax width as the covariate). Results of these experiments show that butterfly wings and beetle horns compete with certain other traits during growth and that the relative sizes of these traits is significantly affected by resource allocation tradeoffs within the developing animal.